Novel syntheses of near-infrared-absorbing di-iminonaphthalene dyes based on cyanoimino derivatives of indoaniline

Abstract

New types of di-iminonaphthalene-type near-1R dyes have been conveniently synthesized by the condensation of 1 -naphthylcyanamide with p-(N, N-dialkylamino)anilines in the presence of an oxidizing agent. The dyes show λ_max 686–779 nm in chloroform, the absorption properties of which are discussed in detail. An intramolecular ring-closure reaction of the acetylamino analogue, N-(2′-acetyl-amino-4′-diethylaminophenyl)-N′-cyano-1,4-naphthoquinone di-imine, under alkaline conditions gave a new benzophenazine dye.